from django.db.models import signals from django.db.models.sql.expressions import SQLEvaluator from django.db.models.fields import Field, BigIntegerField from django.db.models.fields.subclassing import Creator try: from django.db.models.fields.subclassing import SubfieldBase except ImportError: # django 1.2 from django.db.models.fields.subclassing import LegacyConnection as SubfieldBase # NOQA from bitfield.forms import BitFormField from bitfield.query import BitQueryLookupWrapper from bitfield.types import BitHandler, Bit # Count binary capacity. Truncate "0b" prefix from binary form. # Twice faster than bin(i)[2:] or math.floor(math.log(i)) MAX_FLAG_COUNT = int(len(bin(BigIntegerField.MAX_BIGINT)) - 2) class BitFieldFlags(object): def __init__(self, flags): if len(flags) > MAX_FLAG_COUNT: raise ValueError('Too many flags') self._flags = flags def __repr__(self): return repr(self._flags) def __iter__(self): for flag in self._flags: yield flag def __getattr__(self, key): if key not in self._flags: raise AttributeError return Bit(self._flags.index(key)) def iteritems(self): for flag in self._flags: yield flag, Bit(self._flags.index(flag)) def iterkeys(self): for flag in self._flags: yield flag def itervalues(self): for flag in self._flags: yield Bit(self._flags.index(flag)) def items(self): return list(self.iteritems()) def keys(self): return list(self.iterkeys()) def values(self): return list(self.itervalues()) class BitFieldCreator(Creator): """ Descriptor for BitFields. Checks to make sure that all flags of the instance match the class. This is to handle the case when caching an older version of the instance and a newer version of the class is available (usually during deploys). """ def __get__(self, obj, type=None): if obj is None: return BitFieldFlags(self.field.flags) retval = obj.__dict__[self.field.name] if self.field.__class__ is BitField: # Update flags from class in case they've changed. retval._keys = self.field.flags return retval class BitFieldMeta(SubfieldBase): """ Modified SubFieldBase to use our contribute_to_class method (instead of monkey-patching make_contrib). This uses our BitFieldCreator descriptor in place of the default. NOTE: If we find ourselves needing custom descriptors for fields, we could make this generic. """ def __new__(cls, name, bases, attrs): def contribute_to_class(self, cls, name): BigIntegerField.contribute_to_class(self, cls, name) setattr(cls, self.name, BitFieldCreator(self)) new_class = super(BitFieldMeta, cls).__new__(cls, name, bases, attrs) new_class.contribute_to_class = contribute_to_class return new_class class BitField(BigIntegerField): __metaclass__ = BitFieldMeta def __init__(self, flags, default=None, *args, **kwargs): if isinstance(flags, dict): # Get only integer keys in correct range valid_keys = (k for k in flags.keys() if isinstance(k, int) and (0 <= k < MAX_FLAG_COUNT)) if not valid_keys: raise ValueError('Wrong keys or empty dictionary') # Fill list with values from dict or with empty values flags = [flags.get(i, '') for i in range(max(valid_keys) + 1)] if len(flags) > MAX_FLAG_COUNT: raise ValueError('Too many flags') if isinstance(default, (list, tuple, set, frozenset)): new_value = 0 for flag in default: new_value |= Bit(flags.index(flag)) default = new_value BigIntegerField.__init__(self, default=default, *args, **kwargs) self.flags = flags def south_field_triple(self): "Returns a suitable description of this field for South." from south.modelsinspector import introspector field_class = "django.db.models.fields.BigIntegerField" args, kwargs = introspector(self) return (field_class, args, kwargs) def formfield(self, form_class=BitFormField, **kwargs): return Field.formfield(self, form_class, choices=[(k, k) for k in self.flags], **kwargs) def pre_save(self, instance, add): value = getattr(instance, self.attname) return value def get_prep_value(self, value): if isinstance(value, (BitHandler, Bit)): value = value.mask return int(value) # def get_db_prep_save(self, value, connection): # if isinstance(value, Bit): # return BitQuerySaveWrapper(self.model._meta.db_table, self.name, value) # return super(BitField, self).get_db_prep_save(value, connection=connection) def get_db_prep_lookup(self, lookup_type, value, connection, prepared=False): if isinstance(value, SQLEvaluator) and isinstance(value.expression, Bit): value = value.expression if isinstance(value, (BitHandler, Bit)): return BitQueryLookupWrapper(self.model._meta.db_table, self.db_column or self.name, value) return BigIntegerField.get_db_prep_lookup(self, lookup_type=lookup_type, value=value, connection=connection, prepared=prepared) def get_prep_lookup(self, lookup_type, value): if isinstance(value, SQLEvaluator) and isinstance(value.expression, Bit): value = value.expression if isinstance(value, Bit): if lookup_type in ('exact',): return value raise TypeError('Lookup type %r not supported with `Bit` type.' % lookup_type) return BigIntegerField.get_prep_lookup(self, lookup_type, value) def to_python(self, value): if isinstance(value, Bit): value = value.mask if not isinstance(value, BitHandler): # Regression for #1425: fix bad data that was created resulting # in negative values for flags. Compute the value that would # have been visible ot the application to preserve compatibility. if isinstance(value, (int, long)) and value < 0: new_value = 0 for bit_number, _ in enumerate(self.flags): new_value |= (value & (2 ** bit_number)) value = new_value value = BitHandler(value, self.flags) else: # Ensure flags are consistent for unpickling value._keys = self.flags return value class CompositeBitFieldWrapper(object): def __init__(self, fields): self.fields = fields def __getattr__(self, attr): if attr == 'fields': return super(CompositeBitFieldWrapper, self).__getattr__(attr) for field in self.fields: if hasattr(field, attr): return getattr(field, attr) raise AttributeError('%s is not a valid flag' % attr) def __hasattr__(self, attr): if attr == 'fields': return super(CompositeBitFieldWrapper, self).__hasattr__(attr) for field in self.fields: if hasattr(field, attr): return True return False def __setattr__(self, attr, value): if attr == 'fields': super(CompositeBitFieldWrapper, self).__setattr__(attr, value) return for field in self.fields: if hasattr(field, attr): setattr(field, attr, value) return raise AttributeError('%s is not a valid flag' % attr) class CompositeBitField(object): def __init__(self, fields): self.fields = fields def contribute_to_class(self, cls, name): self.name = name self.model = cls cls._meta.add_virtual_field(self) signals.class_prepared.connect(self.validate_fields, sender=cls) setattr(cls, name, self) def validate_fields(self, sender, **kwargs): cls = sender model_fields = dict([ (f.name, f) for f in cls._meta.fields if f.name in self.fields]) all_flags = sum([model_fields[f].flags for f in self.fields], ()) if len(all_flags) != len(set(all_flags)): raise ValueError('BitField flags must be unique.') def __get__(self, instance, instance_type=None): fields = [getattr(instance, f) for f in self.fields] return CompositeBitFieldWrapper(fields) def __set__(self, *args, **kwargs): raise NotImplementedError('CompositeBitField cannot be set.')